The present disclosure relates to a bearing suspension device, and more particularly to a bearing suspension device of variable radial stiffness.
In a rotary machine, a rotary shaft is typically supported by one or more bearings, which, by way of non-exclusive example, may be rolling bearings, oil bearings, or gas bearings. The lifetime of such bearings is strongly dependent on the vibratory characteristics of the rotary machine. Manufacturing imperfections and other parasitic effects can generate unbalances and thus radial vibration acting on the bearings. It is therefore common practice to use devices for absorbing such vibration, at least in part. Thus, in the specification of French patent application published under the No. FR 3 013 760 A1, a device is disclosed that comprises a flexible cage arranged between an outer ring of the bearing and a support for the bearing.
Nevertheless, in such a rotary machine, and in particular in a rotary machine having a rotary shaft that is quite long, such as for example in certain turbomachines, it is possible to encounter resonant phenomena in bending, and in particular the so-called “forward” and “backward” resonant bending modes. Also, in order to be able to cross through such resonant modes without endangering the physical integrity of the rotary machine, bearing suspension devices having variable characteristics have already been proposed. Thus, by way of example, in FR 2 864 995 and FR 2 955 615, two suspension devices are disclosed that have radial stiffnesses that are variable. A temporary change in the radial stiffness of the suspension device of a bearing can thus serve to modify the dynamic response of the rotary machine in transient manner in order to avoid a resonant mode. Nevertheless, those disclosed devices are limited to only two alternative radial stiffnesses.